<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>圆形</title>
    <style>
        canvas {
            background-color: red;
        }
    </style>
</head>

<body>
    <canvas id="tutorial" width="300" height="300">
    </canvas>
    <script>
        // 获取元素
        const canvas = document.getElementById('tutorial')
        // 创建对象
        const context = canvas.getContext('2d')
    </script>
</body>

</html>